It’s probably worth posting in Camelids to get the views of the alpaca fraternity
I’ve heard that a sole alpaca will flock with and therefore protect sheep, but that if there’s more than one alpaca (which there always should be, as a herd animal), they flock together and may or may not provide some deterrence to whatever might attack the sheep. Whether the same would apply to a flock of chickens I have no idea, I’m afraid.
I do know that alpaca temperament can belie the doe-eyed looks, and taking on a couple these large animals is not something that should be undertaken lightly. Not least you have to find someone who can come and shear them annually - and it’s a different kettle of fish to shearing sheep, so you do need to find someone with the experience and equipment.
Sorry you have lost some hens. It’s a terrible shock and one looks at every possibility to protect them, doesn’t one